Analysis of Biogenic Secondary Pollution Materials from Sludge in Surface Waters.

Many countries of the world, including Lithuania, are making an effort to reduce surface water pollution. State monitoring data show that almost 80% of the lakes in Lithuania have an increased amount of sludge. One of the reasons for this increase in sludge is an excessive amount of biogenic material in the water. It is known that even after the source of pollution is removed, the condition of the lake water does not improve; rather, the condition of the lake water worsens due to the secondary pollution of sludge in the water. A study was conducted to determine the impact of secondary sludge pollution on water. For this study, 5 sludge samples were taken from different lakes in Lithuania. Fresh water was poured on the sludge samples, the concentrations of Nt, NO2-N, NO3-N, NH4-N, PO4-P, Pt, the pH and the changes in the electric conductivity (C) were measured in the water within 28 h. Research has shown that the thickness of the sludge layer influences the total amounts of nitrogen, phosphorus, and organic matter present in the sludge. As the thickness of the sludge layer increases in a lake, the total concentrations of nitrogen, total phosphorus and organic matter increase. Studies have also shown that the concentrations of all biogenic substances in water increase, with the exception of total phosphorus. This finding shows that organic phosphorus is "locked" in sludge, and no secondary pollution occurs from this source. Moreover, the electrical conductivity values of the water influence the release of biogenic substances from sludge in the water.

Relation between individual tree mortality and tree characteristics in a polluted and non-polluted environment.

UNLABELLED: Data on individual tree mortality in relatively healthy (Berezinskiy biosphere reserve) and damaged (surroundings of the mineral fertilizer plant 'Achema') even-aged Scots pine (Pinus sylvestris L.) stands are presented. Tree size and competition intensity were found to be the most significant predictors of individual tree mortality in all age groups of the relatively healthy Scots pine stands, however, an essential reduction in the closeness of relations between the tree mortality rate and these variables was determined with the aging of stands. An exponential decrease in tree mortality probability with an increase of tree size is characteristic for trees suffering different competition intensity, however, this decrease becomes much more pronounced as the competition pressure increases. The relations of different tree and stand variables with tree mortality probability have been found to become much weaker in the polluted environment. An exponential increase in tree mortality probability with an increase of crown defoliation was characteristic of damaged Scots pine stands, however, the rate of the increase was different in different age and diameter classes. The impact of crown defoliation on tree mortality rate increased with the aging of stands. At the same defoliation level, individual tree mortality probability was much higher for smaller suppressed trees, however, a relative increase in tree mortality probability along with an increase of crown defoliation was more pronounced for dominant trees. CONCLUSION: a higher mortality of damaged (defoliated) trees should be considered while assessing losses in forest productivity in a polluted environment.

Scots pine (Pinus sylvestris L.) growth and condition in a polluted environment: from decline to recovery.

The results of long-term investigations of Scots pine (Pinus sylvestris L.) growth and condition in the impact zone of one of the biggest air pollution sources in Lithuania--mineral fertilizers plant "Achema" are presented. The main attention is laid to the recovery of damaged stands since annual emissions to air were reduced essentially. The investigations indicated, that the recovery of tree increment was mostly caused by distinct reduction of emissions of nitrogen and sulphur oxides and dust of mineral fertilizers. Despite reduced pollution, crown defoliation of investigated stands has continued to increase for a certain period. After the crown recovery of damaged stands has started, the recovery of most damaged survived trees was most intensive and convergence of defoliated to a different extend stands and trees is characteristic feature of this period. No defoliation threshold has been determined beyond of which recovery of trees would be impossible. Recovery of more than a quarter of damaged trees was registered even in the case of 90% of defoliation. Recovery of dominant trees occurs to be faster of that for suppressed trees within the same level of defoliation. The impact of stand density on the crown recovery rate is negative, the higher density (more intensive competition), the slower recovery of damaged trees. The dependence of growth rate on defoliation was found to be of logistic character: while crown defoliation consists up to 25-30%, tree increment losses are rather inconsiderable, further increase of defoliation leads to the essentially higher increment losses, however having achieved 65-70% defoliation, further increase of defoliation does not result such intensive decrease of radial increment.